Light emitting devices, such as light emitting diodes or laser diodes using group III-V or II-VI compound semiconductor materials, implement light of various colors, such as red, green, blue, and ultraviolet light, due to development of thin film growth techniques and device materials, and implement white light having high efficiency using fluorescent materials or through color mixing.
Due to development such techniques, these light emitting devices are increasingly applied to transmission modules of optical communication units, light emitting diode backlights substituting for cold cathode fluorescent lamps (CCFLs) constituting backlights of liquid crystal display (LCD) devices, illumination apparatuses using white light emitting diodes substituting for fluorescent lamps or incandescent lamps, head lamps for vehicles and traffic lights, as well as to display devices.
Here, an LED has a structure in which a P electrode, an active layer and an N electrode are stacked on a substrate, and current may be supplied to the LED through the P electrode and the N electrode.
When current is applied to the substrate, the current is supplied to the P electrode and the N electrode, and thus holes (+) are discharged from the P electrode to the active layer and electrons (−) are discharged from the N electrode to the active layer. Therefore, as the holes and the electrons are combined in the active layer, the energy level of the active layer is lowered, and the active layer emits energy in a light type simultaneously with lowering of the energy level of the active layer.
When the light emitting device is used in a backlight unit or an illumination apparatus, a light emitting device package in which the light emitting device is mounted may be disposed on a circuit board. Further, in order to achieve electrical contact between the circuit board and the light emitting device package, conductive pads may electrically connect lead frames in the light emitting device package to the circuit board. If the conductive pads are not located at proper positions thereof, a drive signal is not effectively supplied to the light emitting device package, and if a large amount of a pad material is used, the light emitting device package may be inclined on the circuit board.